Search for an onset mechanism that operates for both CMEs and substorms
Search for an onset mechanism that operates for both CMEs and substorms
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DOI：
10.5194/angeo-27-3141-2009
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发表时间：
2009-08
影响因子：
1.9
通讯作者：
G. Siscoe;M. Kuznetsova;J. Raeder
中科院分区：
文献类型：
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作者：
G. Siscoe;M. Kuznetsova;J. Raeder
摘要。亚暴和日冕物质抛射被认为是爆炸能量转换现象的最容易理解的例子，这种现象似乎表征了宇宙等离子体的一种行为模式。这篇论文解决了这两个例子——亚暴和日冕物质抛射——是否支持或不支持爆炸能量转换是在不同地点和不同条件下单一过程的结果这一观点。作为可能对亚暴和日冕物质抛射都有共同作用的候选机制，我们使用福布斯巨灾模型来研究日冕物质抛射，因为在测试之前，它似乎有潜力，经过适当修改，也适用于亚暴。FCM的本质是作用在初始CME上的力的突然不平衡。力的不平衡导致日冕物质抛射开始上升。在日冕物质抛射上升的情况下，有利于磁重联的发生，然后释放日冕物质抛射并协助其排出。因此，FCM的特征是一个暂时有序的序列，其中首先出现力不平衡，导致CME向上（或向外）运动，导致其下的磁重联，从而加速快速驱逐。我们在两个产生亚暴事件的全球磁层MHD模拟的输出中寻找FCM特征。我们发现事件的有序顺序如前所述，但有一个显著的区别：在快速重连开始之前没有等离子体，也就是说，没有与初始CME相对应的东西，在此基础上，力的不平衡作用启动了FCM中的作用。如果这一结果——快速的尾向运动先于次暴扩张的快速重联——最终得到其他研究的证实，则表明对次暴扩张原因的描述应该确定之前快速的尾向运动的原因，因为这必然导致快速的重联，无论重联机制是什么。因此，很明显，确定前面的尾部运动的原因是很重要的。
Abstract. Substorms and coronal mass ejections have been cited as the most accessible examples of the explosive energy conversion phenomenon that seems to characterize one of the behavior modes of cosmic plasmas. This paper addresses the question of whether these two examples – substorms and CMEs – support or otherwise the idea that explosive energy conversion is the result of a single process operating in different places and under different conditions. As a candidate mechanism that might be common to both substorms and CMEs we use the Forbes catastrophe model for CMEs because before testing it appears to have the potential, suitably modified, to operate also for substorms. The essence of the FCM is a sudden onset of an imbalance of the forces acting on an incipient CME. The imbalance of forces causes the CME to start to rise. Beneath the rising CME conditions develop that favor the onset of magnetic reconnection which then releases the CME and assists its expulsion. Thus the signature of the FCM is a temporally ordered sequence in which there is first the appearance of force imbalance which leads to upward (or outward) motion of the CME which leads to magnetic reconnection under it which expedites rapid expulsion. We look for the FCM signature in the output of two global magnetospheric MHD simulations that produce substorm-like events. We find the ordered sequence of events as stated but with a significant difference: there is no plasmoid prior to the onset of rapid reconnection, that is, there is no counterpart to the incipient CME on which an imbalance of forces acts to initiate the action in the FCM. If this result – that rapid tailward motion precedes the rapid reconnection of substorm expansion – is ultimately verified by other studies, it suggests that a description of the cause of substorm expansion should identify the cause of the preceding rapid tailward motion, since this leads necessarily to rapid reconnection, whatever the reconnection mechanism turns out to be. Clearly then, it is important to identify the cause of the preceding tailward motion.